[R-sig-Geo] map algebra with ascii grid

[Denham Robert]

Philip,
      this sounds like an interesting approach.  Do you do anything in
particular to handle larger datasets?  How large are your images?

Robert Denham
Environmental Statistician
Remote Sensing Centre
Telephone 07 3896 9899 
www.nrw.qld.gov.au
 
Department of Natural Resources & Water
QScape Building, 80 Meiers Road, Indooroopilly Qld 4068
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Message: 1
Date: Sun, 15 Jul 2007 07:40:12 -0600
From: Philip Riggs <priggs at cnr.colostate.edu>
Subject: [R-sig-Geo]  map algebra with ascii grid
To: r-sig-geo at stat.math.ethz.ch
Message-ID: <3513F1E2-D6E1-4B2B-89E8-D0B00C2804B7 at cnr.colostate.edu>
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed

>> Dear R Users,
>>
>> could you please advise me on doing map algebra with spatial grids? 
>> It's the first time I am using spatial objects in R. I have imported 
>> an ascii grid file and wanted to round the values in it or sum with a

>> value, but it gives an error message:
>>

>I use Python with Numpy/GDAL python bindings all the time to do spatial
algebra and manipulate grids.
>It has all the math functions, and in the case of categorical data you
can reassign values. Then I
>use rpy to do any statistical analyses in R. You could also do your
manipulation in Python, then 
>save the grid in an appropriate format for import into R to do the
statistical analyses.

> Philip




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